1. Field of the Invention
The present invention generally relates to a radio frequency (RF) device and particularly to a radio frequency device that can achieve high frequency response while maintaining high output impedance and high breakdown voltage.
2. Description of the Related Art
In order to meet the increasing popularity of various wireless communication applications, demands for high-voltage radio frequency devices with high frequency response have correspondingly rapidly increased. Accordingly, with regard to the demands for high-voltage radio frequency devices, achieving high frequency response while maintaining high output impedance and high breakdown voltage is very important. Although conventional asymmetric high-voltage radio frequency devices can achieve high output impedance and high breakdown voltage, the frequency response could not be effectively improved.
Referring to FIG. 1, a conventional high-voltage radio frequency device as illustrated in FIG. 1 primarily includes a semiconductor substrate 100, an n-type doped well 102, a p-type doped region 104, a p-type buried doped region 106, a gate 108, an n-type source region 110 and an n-type drain region 112. The gate 108 includes a gate electrode and a gate dielectric layer (not labeled). The n-type doped well 102 is formed in a surface of the semiconductor substrate 100. The buried doped region 106 is formed in the surface of the semiconductor substrate 100 and adjacent to the n-type doped well 102. The gate 108 is directly formed on the semiconductor substrate 100 and crossing over an interface of the n-type doped well 102 and the buried doped region 106. The n-type source region 110 is formed on a surface of the buried doped region 106 and at a side of the gate 108. The n-type source region 110 and the n-type doped well 102 are isolated from each other by the buried doped region 106. The p-type doped region 104 is formed on the surface of the buried doped region 106 and at a side of the n-type source region 110 far away from the gate 108. The buried doped region 104 can be connected or disconnected to the n-type source region 110. The n-type drain region 112 is formed in a surface of the n-type doped well 102 and at another side of the gate 108.
However, although the above-mentioned high-voltage radio frequency device can effectively improve the output impedance and breakdown voltage, since an area occupied by the gate is excessively large, it could not effectively improve frequency response.